Dynamic Inter-Cell Interference Estimation for Flash Memory
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Solution Overview
Problem
Conventional methods for mitigating inter-cell interference (ICI) in flash memory rely on static ICI parameters, which fail to account for variations throughout the life of a solid-state drive (SSD) and across different physical locations, leading to suboptimal results.
Innovation Solution
A method and apparatus that estimate ICI parameters on-demand using pattern-dependent histograms, allowing for real-time mitigation of ICI by processing read and program operations across multiple memory units and aggressor cells, eliminating the need for offline characterization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If static ICI parameters are used for mitigation, then the system complexity is reduced, but the reliability of data storage deteriorates due to inability to account for variations throughout SSD life and across different physical locations
Solution Approach 1:
The patent transforms the static ICI parameter approach into a dynamic one by implementing on-demand estimation that adapts to varying conditions throughout the SSD lifecycle and across different physical locations. The controller dynamically generates ICI parameters based on current read operations and observed interference patterns, allowing the system to respond to changing conditions without requiring complex offline characterization procedures for each scenario.
Solution Approach 2:
The system performs self-characterization by automatically estimating ICI parameters during normal read operations without requiring external offline characterization procedures. The controller uses observed data from read operations to generate interference parameters on-demand, enabling the system to self-adapt to variations in interference conditions throughout its operational life.
2Measurement precision
If offline characterization procedures are used to estimate ICI parameters, then the measurement precision is improved, but the loss of time increases due to dedicated characterization procedures and static configuration
Solution Approach 1:
The patent performs preliminary estimation of ICI parameters by leveraging data from previous read operations. The controller maintains and updates ICI parameter estimates based on observed interference patterns, so that when new read operations occur, the parameters are already available or can be quickly updated, eliminating the need for time-consuming offline characterization procedures at the time of data access.
Solution Approach 2:
The system continuously updates ICI parameter estimates during normal read operations rather than performing discrete offline characterization. The controller continuously monitors interference patterns and refines parameter estimates based on ongoing operations, ensuring that accurate parameters are always available without interrupting the normal flow of read operations for dedicated characterization.
3Ease of operation
If pre-defined ICI parameters are configured statically, then the ease of operation is improved, but the adaptability deteriorates because parameters cannot account for variations across pages, blocks, dies, and throughout SSD life
Solution Approach 1:
The patent implements local quality by generating ICI parameters specific to each read operation context, including the particular page, block, and die being accessed. The controller determines interference parameters based on the specific aggressor patterns and victim cell conditions for each local context, rather than applying uniform pre-defined parameters across all operations. This allows the system to maintain ease of operation through automated per-context parameter generation while achieving high adaptability to local variations.
4Reliability
If on-demand ICI parameter estimation is implemented, then the reliability is improved by accounting for variations, but the device complexity increases due to real-time processing requirements
Solution Approach 1:
The patent achieves universality by designing the controller to perform multiple functions: it executes read operations, monitors interference patterns, estimates ICI parameters, and applies mitigation all within a single integrated system. The same controller hardware and firmware that manage normal read operations also perform the sophisticated real-time parameter estimation, eliminating the need for separate dedicated characterization equipment or complex external systems.
Solution Approach 2:
The controller performs self-characterization and self-adjustment by automatically generating ICI parameters based on observed interference patterns during normal operations. This self-service capability allows the system to achieve high reliability through adaptive parameter estimation without requiring complex external characterization systems or manual configuration procedures.
Data Source
AI summary
An apparatus comprising a memory and a controller. The memory may be configured to process a plurality of read/program operations. The memory may comprise a plurality of memory units each having a size less than a total size of the memory. The controller may be configured to perform a plurality of reads on a victim cell. The controller may be configured to store measured victim information from the plurality of reads on the victim cell. The controller may be configured to perform one or more reads on a plurality of aggressor cells. The controller may be configured to store measured aggressor information from the one or more reads on the plurality of aggressor cells. The controller may be configured to generate inter-cell interference parameters based on the measured victim information and the measured aggressor information. The controller may be configured to mitigate inter-cell interference based on the inter-cell interference parameters.